A rotary mower of this general type is known the drive means of which are housed in the beam and consist of pulleys keyed on said shafts directed upwardly and driven by a belt. These drive means do not make it possible to assure a synchronous driving of the cutting elements. The belt can slide on the pulleys during the working of the rotary mower when a cutting element which is driven by a pulley is braked or locked for a certain period of time for any reason (such as encounters with obstacles, heavy bundles of fodder, etc.). When the desynchronization between two adjacent cutting elements reaches a certain value, the cutting tools mounted on these cutting elements can collide if they are located on the same level. These collisions can cause breaking of the cutting tools or their fastenings.
Considering the high rotating speed of the cutting elements, a broken cutting tool or one torn from its cutting tool support can cause serious accidents to persons who are close to the rotary mower or even to the operator. Moreover, a cutting element that is equipped with a broken cutting tool or on which a cutting tool is missing performs unsatisfactory work.
To mitigate this serious drawback, the known rotary mower has each two adjacent cutting elements offset vertically in relation to one another so as to rotate in two different planes. Thus, the cutting tools of two adjacent cutting elements can no longer collide with one another even if the positions of the cutting elements are desynchronized.
The drawback of this known rotary mower resides in the fact that the space of the upper part of the beam located under the cutting elements rotating in a high plane of rotation and the space of the upper part of the beam not swept by the cutting tools of the neighboring elements rotating in a low plane of rotation both become fouled. This fouling of the upper part of the beam is not acceptable. On the one hand, it can impede the flow of cut fodder toward the rear and, on the other hand, it can impede the cutting itself if the fouling progresses forward into the working zone of the cutting tools.